We calculate the energy of the 2D material relative to the convex hull of competing bulk phases, \(\Delta H_{\text{hull}}\) . The convex hull is currently constructed from the 2836 most stable binary bulk compounds which were obtained from the OQMD[1]}. The energies of the bulk phases were recalculated with GPAW using the PBE xc-functional and the same numerical settings as applied for the 2D materials (but the structure was not re-optimised). Because the bulk reference structures from OQMD were optimised with the VASP code and with Hubbard \(U\) -corrections for materials containing 3\(d\)  elements, and because the PBE misses attractive vdW interaction, the bulk energies could be slightly overestimated relative to the monolayers. As a consequence, monolayers that also exist in a layered bulk phase could have \(\Delta H_{\text{hull}}<0\) , even if the layered bulk phase is part of the convex hull and thus should be energetically more stable than the monolayer. Comparing our \(\Delta H_{\mathrm {hull}}\)  values for 35 compounds with the exfoliation energies calculated in Ref. mounet2016novel employing vdW compliant xc-functionals for both bulk and monolayer, we estimate the errors in the convex hull energies to be below 0.1 eV/atom.
